The 3rd Generation Partnership Project, 3GPP, is responsible for the standardization of the Universal Mobile Telecommunication System, UMTS, and Long Term Evolution, LTE. The 3GPP work on LTE is also referred to as Evolved Universal Terrestrial Access Network, E-UTRAN. LTE is a technology for realizing high-speed packet-based communication that can reach high data rates both in the downlink and in the uplink, and is thought of as a next generation mobile communication system relative to UMTS. In order to support high data rates, LTE allows for a system bandwidth of 20 MHz, or up to 100 MHz when carrier aggregation is employed. LTE is also able to operate in different frequency bands and can operate in at least Frequency Division Duplex, FDD and Time Division Duplex, TDD, modes.
The 3GPP began in 2006 to define the requirements of a Public Warning System, PWS. An effective Public Warning System is an essential part of an effective early warning system and can substantially reduce deaths and damage from certain disasters by giving the population time to flee for example a tsunami, flood or severe storm, to prepare for an earthquake and to enable them to protect their property wherever possible. The technical specification for PWS gives general criteria for the delivery of alerts, the content of messages and user equipment features of PWS-capable user equipment, UE. There are regional systems of PWS; for example the Earthquake and Tsunami Warning System (ETWS) in Japan and Commercial Mobile Alert System (CMAS) in the USA. The technical specification also includes the requirements of these regional systems.
The 3GPP standards for PWS are 3GPP TR 22.968 Rel-12 SP-2014-09-17 “Study for Requirements for Public Warning system (PWS) Service” and 3GPP TS 22.268 Rel-12 SP-65 2014-09-17 “Public Warning System (PWS) Requirements”. The alerting technology to be used is not specified but Cell Broadcast Service is the generally used technology for PWS.
It is essential that as many user equipment as possible receive these PWS messages. Hence, there is a need for techniques for further enhancing reliability of reception of PWS messages.